Direct current (DC) offsets often appear in electronic circuits that process electrical signals. When the DC offsets are large enough, they may interfere with proper processing of electrical signals. Additionally, changes in the DC offsets, such as changes that may occur over an operating temperature range or with power supply voltage variations, may be problematic. One method to reduce the impact of DC offsets is to interrupt processed electrical signals and then measure and compensate for DC offsets. However, in some circuits interruption of processed electrical signals may not be possible. For example, in a radio frequency (RF) communications terminal, an RF transmitter may continuously transmit an RF transmit signal, such as in a single-carrier frequency division multiple access (SC-FDMA) communications system or other fourth generation (4G) system, or as in a wideband code division multiple access (WCDMA) communications system or other third generation (3G) system. It may not be possible to interrupt such an RF transmit signal to make DC offset measurements of circuitry influenced by the RF transmit signal.
Furthermore, an RF communications terminal may use a DC power detector to measure the transmit power associated with a continuously transmitted RF signal. The DC power detector may have a DC offset that may affect measurements of the transmit power, particularly at low power levels. If the continuously transmitted RF signal may not be interrupted so that the DC offset can be measured, another way to determine the DC offset is needed. Similarly, the RF communications terminal may have an RF receiver, which may have a DC offset and may be influenced by the continuously transmitted RF signal. If the continuously transmitted RF signal may not be interrupted so that the DC offset of the RF receiver can be measured without the influence of the continuously transmitted RF signal, another way to determine the DC offset is needed.